ArrayFunctionsES5.js

var primaryColors = [
  {color: 'red'},
  {color: 'yellow'},
  {color: 'blue'}
];
 
var result = primaryColors.reduce(function(previous, primaryColor) {
  previous.push(primaryColor.color);
    return previous;
}, []); 
console.log(result); 
//output 
["red", "yellow", "blue"]